The propagation of a mode of radiation in a lossy channel corresponds to the
coupling of the mode \(a\)  with a zero temperature reservoir made of large
number of external modes. By assuming a Markovian reservoir and weak coupling
between the system and the reservoir the dynamics of the system is described
by the Lindblad Master equation [1]}
\(\dot{\rho }=\frac{\Gamma }{2}\mathcal {L}[a]\rho \) 
